The present invention relates to an apparatus for the regulation of the fuel-air mixture delivered to an internal combustion engine by the variation of those crosssectional areas of a carburetor, having a fixed venturi, which influence the fuel apportionment in accordance with parameters characterizing the operational behavior of the internal combustion engine.
In a well-known apparatus of this kind, one or several bypass conduits which can be opened or closed by an electromagnetic valve are provided in parallel with the main fuel orifice of a carburetor fixture. The opening occurs by means of pulses of fixed frequency and differing duration, whereby these given durations of the opened state are variable in accordance with operational parameters of the internal combustion engine.
An apparatus wherein the fuel apportioning section can be supplied through electrically switched valves with fuel having differing pressure levels is also well known. In this apparatus, float chambers featuring differing filling heights serve as the fuel supply source.
These apparatuses entail the disadvantage that the apportioned fuel flow variations take place abruptly. An integration of the fluctuations of the apportioned fuel quantity caused by the constantly changing regulation amplitude, in the sense of an analog variation of this apportioned quantity, which process avoids the strong fluctuations caused by spurious influences, is impossible with these devices. In addition, in the last apparatus described, only a small pressure difference is available for the regulation interaction, so that the desired quantitative variation can be accomplished only relatively slowly.
In addition, in well-known regulation devices the air pressure in the float chamber of a carburetor is regulated by means of connecting the air space of the float chamber alternately with pressure sources of a respectively higher or lower pressure level. The pressures utilized herein are the air pressure respectively in the suction tube upstream of the venturi, and that within the most constricted cross-sectional area of the venturi of the carburetor. This arrangement entails the disadvantage that the available pressures are subject to pulsations, and also that the pressure levels, i.e., the available pressure differences, are dependent upon the given operational condition of the internal combustion engine. Moreover, air is a compressible medium, which, if used as a transmitting link, can easily break into oscillations, so that regulation carried on in this manner can be influenced derogatorily, and supplemental measures must be taken to prevent these oscillations, i.e., to compensate for these influences.